Field
Aspects of the present disclosure relate generally to variable gain amplifiers, and more particularly, to a variable gain amplifier with improved power supply noise rejection.
Background
A variable gain amplifier (VGA) may be configured to apply a gain-frequency response to an input differential signal to generate an output differential signal. The gain-frequency response is typically set or adjusted via a variable capacitor and a variable resistor coupled in parallel between sources of input differential field effect transistors (FETs) of the VGA. The input differential signal is applied to the gates of the input differential FETs, respectively. The output differential signal is generated at the drains of the input differential FETs, respectively.
In such VGA configuration, it is desirable to reduce noise emanating from a supply voltage rail from propagating into the signal path of the VGA. Additionally, it is desirable to reduce area on an integrated circuit (IC) to implement the variable capacitor of the VGA. Further, it is desirable to reduce wiring parasitic associated with connecting the variable capacitor to the sources of the input differential FETs to achieve a better control and desirable gain-frequency response for the VGA.